11 – linking innate & adaptive:Visualizing antigen presentation Flashcards
DCs can present multiple
antigens at once
run down of DC activation
PRRs are activated in periphery tissues –> then DC gets activated & presents the MHC peptides to T cells in lymph node
Selectin
adhesion molecules
Weak binding –> rolling
Chemokine binding chemokine receptors
CCL19n & CCL21 bind to CCR7 on lymphocytes
Lead to activation & change conformation of integrins
Integrin
adhesion molecule
Binding causes:
tight binding – rolling stops
Lymphocytes migrate - diapedesis
Selectins involved in & how does it work
leukocyte homing
Light attachment of selection on T cells to HEV –> result ion T cell rolling along endothelial surface
Target them to lymphoid tissue
Different tissues express … examples?
different molecules
HEV – lymph nodes
Mucosal epithelium – Peyer’s patch
steps of lymphocyte entering lymph node
1.Circulating lymphocyte enter high endothelial venule in lymph node
2.Rolling – mediated by selectins
3.Activation – by chemokines
- Arrest & tight binding (Adhesion) - mediated by integrin interaction
5.Diapedesis – trans endothelial migration
Lymphocyte crosses the endothelium and enter lymph node
Once in lymph node – t cells scan for
antigens
DCs can secrete … once in lymph node
chemokines to attract T cells to them
Once Ag encountered – long … why?
T cell/DC interaction
Naive T cells arrest their movements after engaging Ag:MHC
-T cells bind to DC & slow down their movcement through lymph node
Kinetics of early encounters depensd on: 4
Quality
Quantity
Availability of Ag
Actiavtion state of a DC
T cells become involved in
committed & long term relationship with DCs
8 hours or more
what is Immunological synapse
interaction with 2 cells
DC can be surveyed by more than…
5000 T cells/h
T cells can spend … doing what?>
1-24hr circulating & looking for their antigen
T cells can experience proliferation & differentiation over
~4 days
immune system is
dynamic /not linear
-Constantly dealing with microinjury/tissue repair/microbiota
-Many events happen in parallel many processes overlap over time
-Can change location & influence each other
T cells
-Types of lymphocytes
-Arise in thymus from bone bone-marrow progenitors
-Most adaptive immune responses require activation of T cells
T cells can ONLY recognize
peptide fragments of the Ag bound to self-molecules of MHC
MHC – major histocompatibility complex
Peptide-MHC complexes are expressed on
on plasma membrane of APC (antigen-presenting cells)
Lymphocytes appear similar
but different sets carry
different clusters of differentiation (CD) co-receptor on their surface
CD8+ T cells
once activated with 3 signals:Become effector Cytotoxic T lymphocytes (CTLs)
CD4+ Helper T cells
can be divided into distinct subsets once receives all 3 signals
-secrete cytokines with different roles
subset of CD4+
(5)
TH1
TH2
TH17
TREG
TFH
Each produces distinct cytokine profile & regulates distinct activities within the body
Activation of CD8+ T cells
CD8+ T cells recognize Ag on MHC I
Activation of CD4+ T cells
CD4+ T cells recognize Ag on MHC II
Activation signals sent to T cells are highly dependent on
PAMP that DC has been exposed to
Influence the type of cytokines produced
Leads to type of effector T cell hat will arise
Different PAMP on PRR –>
Different cytokines –> Different effector T cells
